Numerical study of the influence of material density of dispersed inclusions on the process of gas-suspension splitting in vacuum

В работе моделируется течение однородного газа и неоднородной среды. Целью работы является изучение влияния размера частиц дисперсной компоненты смеси на истечение дисперсной среды в вакуум и выявление отличий от процесса истечения в вакуум однородного газа. Математическая модель, примененная в данной работе, реализует континуальную методологию моделирования течения неоднородной среды, такого рода методика моделирования движения смеси предполагает решение полной гидродинамической системы уравнений движения для каждой из компонент смеси, системы уравнений движения компонент смеси связаны слагаемыми, отвечающими за межфазное силовое и тепловое взаимодействие. Система уравнений включает уравнения непрерывности для плотности несущей среды и средней плотности дисперсной компоненты смеси. Для описания сохранения импульса несущей среды решалось уравнение Навье-Стокса, для дисперсной компоненты смеси также записывалось уравнение сохранения импульса с учетом слагаемых отвечающих за межкомпонентное взаимодействие. Уравнения сохранения энергии компонент смеси решались с учётом межкомпонентного теплообмена. Система уравнений математической модели дополненная краевыми условиями решалась явным конечно-разностным методом второго порядка точности. В результате моделирования выявлены отличия в распределении параметров сплошной среды при распространении в вакуум чистого газа и газовой взвеси частиц. Также выявлено влияние размера частиц дисперсной фазы на процесс истечение несущей среды и дисперсной компоненты газовзвеси в вакуум. The work simulates the flow of a homogeneous gas and an inhomogeneous medium. The aim of the work is to study the influence of the particle size of the dispersed component of the mixture on the outflow of the dispersed medium into vacuum and to identify differences from the process of outflow of a homogeneous gas into the vacuum. The mathematical model used in this work implements a continuous methodology for modeling the flow of an inhomogeneous medium, this kind of methodology for modeling the mixture motion involves solving the complete hydrodynamic system of equations of motion for each of the components of the mixture, the systems of equations of motion of the components of the mixture are connected by terms responsible for the interphase force and thermal interaction. The system of equations includes continuity equations for the density of the carrier medium and the average density of the dispersed component of the mixture. To describe the momentum conservation of the carrier medium, the Navier-Stokes equation was solved for the dispersed component of the mixture, the equation of momentum conservation was also written taking into account the terms responsible for the intercomponent interaction. The energy conservation equations for the mixture components were solved taking into account inter-component heat transfer. The system of equations of the mathematical model supplemented by boundary conditions was solved by an explicit finite-difference method of the second order of accuracy. As a result of the simulation, differences in the distribution of the parameters of a continuous medium during the propagation of pure gas and gas suspension of particles into a vacuum are revealed. The effect of the particle size of the dispersed phase on the process of the outflow of the carrier medium and the dispersed component of the gas suspension into vacuum was also revealed.

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Specimen Collection Effect in Scanning Electron Microscopy Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095492 ◽

1972 ◽

Vol 30 ◽

pp. 448-449

Author(s):

J. Temple Black ◽

Jose Guerrero

Keyword(s):

Surface Morphology ◽

Secondary Electron Emission ◽

Secondary Electrons ◽

Charge Effects ◽

Material Density ◽

Specimen Collection ◽

The Subject ◽

Curved Paths ◽

Subject Material ◽

Microscopy Images

In the SEM, contrast in the image is the result of variations in the volume secondary electron emission and backscatter emission which reaches the detector and serves to intensity modulate the signal for the CRT's. This emission is a function of the accelerating potential, material density, chemistry, crystallography, local charge effects, surface morphology and especially the angle of the incident electron beam with the particular surface site. Aside from the influence of object inclination, the surface morphology is the most important feature In producing contrast. “Specimen collection“ is the name given the shielding of the collector by adjacent parts of the specimen, producing much image contrast. This type of contrast can occur for both secondary and backscatter electrons even though the secondary electrons take curved paths to the detector-collector.Figure 1 demonstrates, in a unique and striking fashion, the specimen collection effect. The subject material here is Armco Iron, 99.85% purity, which was spark machined.

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Numerical study of the low-frequency atomic dynamics in a Lennard-Jones glass

Philosophical Magazine B ◽

10.1080/014186398259572 ◽

1998 ◽

Vol 77 (2) ◽

pp. 473-484 ◽

Cited By ~ 3

Author(s):

M. Sampoli, P. Benassi, R. Dell'Anna,

Keyword(s):

Numerical Study ◽

Low Frequency ◽

Lennard Jones

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